Field of the Invention
The present invention relates to wireless communications, and more particularly, to a method and apparatus for performing a mobility management (MM) attach and service request procedure for a network slice based new radio access technology (NR or new RAT) in a wireless communication system.
Related Art
3rd generation partnership project (3GPP) long-term evolution (LTE) is a technology for enabling high-speed packet communications. Many schemes have been proposed for the LTE objective including those that aim to reduce user and provider costs, improve service quality, and expand and improve coverage and system capacity. The 3GPP LTE requires reduced cost per bit, increased service availability, flexible use of a frequency band, a simple structure, an open interface, and adequate power consumption of a terminal as an upper-level requirement.
Work has started in international telecommunication union (ITU) and 3GPP to develop requirements and specifications for new radio (NR) systems. The NR system may be called another name, e.g. new radio access technology (new RAT). 3GPP has to identify and develop the technology components needed for successfully standardizing the NR timely satisfying both the urgent market needs, and the more long-term requirements set forth by the ITU radio communication sector (ITU-R) international mobile telecommunications (IMT)-2020 process. Further, the NR should be able to use any spectrum band ranging at least up to 100 GHz that may be made available for wireless communications even in a more distant future.
The NR targets a single technical framework addressing all usage scenarios, requirements and deployment scenarios including enhanced mobile broadband (eMBB), massive machine-type-communications (mMTC), ultra-reliable and low latency communications (URLLC), etc. The NR shall be inherently forward compatible.
Initial work for NR should allocate high priority on gaining a common understanding on what is required in terms of radio protocol structure and architecture, with focus on progressing in radio interface protocol architecture and procedures and radio access network architecture, interface protocols and procedures. This work shall cover at least the followings:                Study the feasibility of different options of splitting the architecture into a “central unit (CU)” and a “distributed unit (DU)”, with potential interface in between, including transport, configuration and other required functional interactions between these nodes;        Study the alternative solutions with regard to signaling, orchestration . . . and operations, administration and maintenance (OAM), where applicable;        Study and outline the radio access network (RAN)-core network (CN) interface and functional split;        Study and identify the basic structure and operation of realization of RAN networks functions (NFs); Study to what extent it is feasible to standardize RAN NFs, the interfaces of RAN NFs and their interdependency;        Study and identify specification impacts of enabling the realization of network slicing;        Study and identify additional architecture requirements, e.g. support for quality of services (QoS) concept, self-organization network (SON), support of sidelink for device-to-device (D2D).        
In the above listed items, features of network slicing should be supported in detail.